I ran into an instance today wherein I needed to validate that a boolean field was either true or false and not null. I tried using validates :fieldname, :presence => true, but since :presence uses #blank? under the hood, it was reading false as not being present. (Why is false considered blank?)

Anyway, I needed a validator to test whether an attribute was either true or false and I couldn’t find anything among the standard validators, so I wrote my own.

Just plop this file in your app’s lib/validators directory.

class TruthinessValidator < ActiveModel::EachValidator
  def validate_each(record, attribute, value)
    unless value == true || value == false
      record.errors[attribute] << "must be true or false"

In your model, add the validation like so:

class SomeModel < ActiveRecord::Base

  validates :field_name, :truthiness => true


For more information on writing validators, see Getting Started with Custom Rails3 Validators.

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About me

I live in the greater Kansas City area with my beautiful wife, our two great kids, and our dog. I've been programming using Open Source technologies since '97 and I'm currently an independent software developer specializing in Ruby on Rails and iOS. I am for hire.

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